Plasma Retinol Binding Protein

Modified Dose Response Dehydro retinol/retinol  

Sources International Vitamin A Consultative Group, 1983 Underwood, 1 990. 

2 Plasma Retinol Binding Protein Measurement of plasma concentrations of RBP may give some additional information. Indeed, it has been suggested that because retinol is susceptible to oxidation on storage of blood samples, measurement of RBP may be a better indication of the state of vitamin A status. In adequately nourished subjects, about 13% of immunologi-cally reactive RBP in plasma is present as the apo-protein, whereas in vitamin A-deficient children, the proportion of apo-protein may rise to 50% to 90% of 

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Figure S.3 Schematic diagram of the structure of human plasma retinol-binding protein (RBP), which is an up-and-down P barrel. The eight antiparallel P strands twist and curl such that the structure can also be regarded as two p sheets (green and blue) packed against each other. Some of the twisted p strands (red) participate in both P sheets. A retinol molecule, vitamin A (yellow), is bound inside the barrel, between the two P sheets, such that its only hydrophilic part (an OH tail) is at the surface of the molecule. The topological diagram of this stmcture is the same as that in Figure 5.2. (Courtesy of Alwyn Jones, Uppsala, Sweden.)...

Figure S.S Amino acid sequence of p strands 2 3 4 in human plasma retinol-binding protein. The sequences are listed in such a way that residues which point into the barrel are aligned. These hydrophobic residues are arrowed and colored green. The remaining residues are exposed to the solvent.

Papiz, M.Z., et al. The structure of p-lactoglobulin and its similarity to plasma retinol-binding protein. Nature 324 383-385, 1986. 

Figure 4.13 Anatomy of selected proteins. (A) The /3 subunit of hemoglobin carrying a heme molecule (B) triose isomerase and (C) /3-lactoglobulin carrying a molecule of vitamin A. Spirals represent helix segments, and the broad arrows are pleated sheet polypeptide segments showing the direction from the N to the C terminus. (A and B reproduced with permission from Richardson JS. The anatomy and taxonomy of protein structure. Adv Prot Chem 34 168-339, 1981. C reproduced with permission from Papiz MZ, Sawyer L, Eliopoulos EE, North ACT, Findlay JBC, Sivaprasadarao R, Jones TA, Newcomer ME, Kraulis PJ. The structure of beta-lactoglobulin and its similarity to plasma retinol-binding protein. Nature 324 383-385, 1986.)...

The overall folding of /3-LG is remarkably similar to that of human plasma retinol-binding protein (Papiz et al., 1986). The core is made up of an eight-stranded antiparallel /3 sheet, which forms a /3 barrel. There is also a short a helix at the C terminus. As described by Monaco et al. (1987), the interior of the /3 barrel is essentially hydrophobic. The conformational difference between the A form and B form of the protein is not significant. The most interesting observation is that the bound retinol molecule interacts with the protein in a way completely different from that of serum retinol-binding protein. The calculated difference map showed that the molecule is not located in the central j3 barrel but binds to the a-heIix//3-barrel interface delimited by about 15 residues. Most of the... 

Soprano DR, Blaner WS. Plasma retinol-binding protein. In Sporn MB, Roberts AS, Goodman DS, editors. The retinoids, 2 edition. New York Raven Press, 1994 257-81. 

Brouwer, A., W.S. Blaner, A. Kufcler and K.J. Van Den Berg. Study on the mechanism of interference of 3,4, 3, 4 -tetrachlorobiphenyl with the plasma retinol-binding proteins in rodents. Chem.-Biol. Interact. 68 203 -217, 1988. 

Berni, R., M. Stoppini and M.C. Zapponi. The piscine plasma retinol-binding protein. Purification, partial amino acid sequence and interaction with mammalian transthyretin. Eur. J. Biochem. 204 99-106, 1992. 

The first lipocalin whose 3-D structure was solved and refined at high resolution was the human plasma retinol-binding protein (RBP) [22, 23]. RBP acts as a natural transporter of vitamin A (retinol) in the blood of vertebrates. Upon complexation in a hydrophobic cavity with complementary shape, the poorly soluble terpenoid alcohol becomes packaged by the protein and protected from oxidation or double-bond isomerization. RBP is synthesized in the liver and directly loaded with fhe hgand in fhe hepatocyte, where retinol is stored. Furthermore, the holo-RBP forms a structurally defined ternary complex with transthyretin [24], also known as prealbumin. After delivery of the retinol ligand to a target tissue, fhe complex decomposes and fhe monomeric apo-RBP becomes filtered out by fhe kidney and degraded. 

During absorption some /3-carotene is also converted to retinoid (Dimitrov et al, 1988 Olson, 1989 van Vliet et al, 1992 Scita et al, 1993) and transferred via a plasma chylomicron (renmant) retinyl ester compartment to a liver retinyl ester compartment. From here it is released in a plasma retinol-binding protein-retinol (RBP-ROH) compartment for transfer to target tissues. Eventually it is lost irreversibly from the RBP-ROH compart-... 

The predicted chylomicron retinyl-d4 ester curve is characterized by a sharp peak similar to that of the /3-carotene-dg, again in accord with the expected rapid clearance of chylomicrons foUowing a meal. The predicted plasma retinol-binding protein-retinol-d4 curve shows an initial rise and fall, then a sustained level of retinol-d4 after the /3-carotene-dg dose. This is very similar in shape to that seen when the same subject ingested retinyl-d4 acetate in a previous experiment (Song et oL, 1995). The sustained level of retinol-d4 is a result of the slow release of retinoid into the plasma from... 

Rat cellular retinol binding Protein c-RBP Bovine plasma retinol-binding protein (bRBP)... 

Blaner, W. S. and Goodman, D. S. 1990. Purification and properties of plasma retinol-binding protein. Methods Enzymol 189 193-206. 

Bobbert, P, Weithauser, A., Andres, J. et al. 2009. Increased plasma retinol binding protein 4 levels in patients with inflammatory cardiomyopathy. Eur J Heart Fail 11 1163-1168. Broch, M., Gomez, J. M., Auguet, M. T. et al. 2010. Association of retinol-binding protein-4 (RBP4) with lipid parameters in obese women. Obes Surg 20 1258-1264. 

Cho, Y. M., Youn, B. S., Lee, H. et al. 2006. Plasma retinol-binding protein-4 concentrations are elevated in human subjects with impaired glucose tolerance and type 2 diabetes. 

Makino, S., Fujiwara, M., Suzukawa, K. et al. 2009. Visceral obesity is associated with the metabolic syndrome and elevated plasma retinol-binding protein-4 level in obstructive sleep apnea syndrome. Horm Metab Res 41 221-226. 

Raila, J., Henze, A., Spranger, J. et al. 2007. Microalbuminuria is a major determinant of elevated plasma retinol-binding protein 4 in type 2 diabetic patients. Kidney Inti 72 505-511. 

Sasaki, M., Otani, T., Kawakami, M. et al. 2010. Elevation of plasma retinol-binding protein 4 and reduction of plasma adiponectin in subjects with cerebral infarction. Metabolism 59 527-532. 

Soprono, D. R. and Blaner, W. S. 1994. Plasma retinol-binding protein. In The Retinoids Biology, Chemistry and Medicine, M. B. Spom, A. B. Roberts, and D. S. Goodman, eds. Raven Press, New York 257-282. 

Plasma Retinol-Binding Protein DeWitt S. Goodman... 

The peculiar spectral properties of CRBP-bound retinol and RME are indicative of specific ligand-protein interactions (see Fig. 2) Instead, other holo-retinoid-binding proteins exhibit less characteristic spectra. For example the absorption spectrum of the complex of retinol with plasma retinol-binding protein (RBP) is characterized by a single, well-shaped peak centered at approx 328 nm On the other hand, the absorption spectra of some CRBP-bound retinoids, like CRBP-bound a l-trans retinal (12,13), do not resemble those of CRBP-bound retinol and RME. 

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